Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 221538
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
938 AM MDT MON SEP 22 2014

.UPDATE...
ISSUED AT 930 AM MDT MON SEP 22 2014

15Z SURFACE ANALYSIS HAD TROUGH FROM AB INTO NORTH CENTRAL WY.
WATER VAPOUR HAD UPPER LOW SPINNING OVER CENTRAL ID WITH LEAD
SHORTWAVE OVER NORTHWEST CO. THIS WAVE WILL SPIN NORTHEAST TODAY
AS UPPER LOW SLIDES EAST. INCREASING LIFT AHEAD OF SHORTWAVE IS
EXPECTED...BUT PRECIPITATION NOT LIKELY TO START UNTIL THE
AFTERNOON GIVEN DRY AIR IN THE MID-LEVELS PER 12Z KUNR SOUNDING
AND MLCIN. SHRA/TSRA WILL ADVECT/DEVELOP INTO THE SOUTHERN HALF OF
THE CWA THROUGH THE AFTERNOON HOURS AND THEN SHIFT EAST TONIGHT.
GUIDANCE EVEN LESS CONDUCIVE TO MUCH IN THE WAY OF PRECIPITATION
EXCEPT FOR THE HIGHER TERRAIN DURING PEAK HEATING AND SOUTHEAST
OF THE BLACK HILLS TONIGHT WHERE LOW LEVEL JET DEVELOPS. GIVEN
INCREASING GRADIENT AHEAD OF SURFACE FEATURES...HAVE BUMPED WINDS
UP ON THE SD PLAINS THIS AFTERNOON.

UPDATE TO ADDRESS PRECIPITATION TIMING AND WINDS COMING SOON.

&&

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
ISSUED AT 219 AM MDT MON SEP 22 2014

CENTRAL ROCKIES UPPER LEVEL CLOSED LOW WILL ADVECT THROUGH THE
REGION IN THE PERIOD...SUPPORTING SOME CHANCES FOR RAIN ACROSS
MOST OF THE AREA...ALBEIT A SMALL CHANCE MOST AREAS. DEPARTING SFC
RIDGE HAS LEFT A SIG DRY WEDGE ACROSS THE REGION...HIGHLY LIMITING
PRECIP CHANCES UNTIL POS THETA-E ADV PROCESSES CAN SIG INCREASE BL
MOISTURE LATE THIS AFTERNOON PER STAUNCH LL SOUTHERLY FLOW.
QUICKER EXIT AND LACK OF APPRECIABLE INSTABILITY AND WIDESPREAD
FORCING FOR ASCENT WILL LIMIT PRECIP CHANCES TO MAINLY SCENTRAL SD
WHERE THE BEST OVERLAP OF THESE FEATURES ALONG WITH DEEPER
MOISTURE WILL BE. MAIN CHANGE TO THE PREVIOUS FORECAST WAS TO
ADJUST POPS DOWN ACROSS THE AREA...ESP IN THE TUES PERIOD WHEN
LARGE SCALE SINK WILL SPREAD NW-SE OVER THE REGION.

TODAY/TONIGHT...INCREASING MID AND HIGH CLOUD CAN BE EXPECTED AS THE
PROPAGATING CENTRAL ROCKIES UPPER LOW SHIFTS EAST...SUPPORTING A
BAND OF ELEVATED POS THETA-E ADV. DRY LL PROFILES AND HIGH CENTERED
LIFT WILL LIMIT PRECIP TO SPRINKLES THROUGH MORNING WESTERN
AREAS...AND SO HAVE RETAINED LOW POPS THERE. DIURNAL HEATING WILL
LEAD TO A SMALL UPTICK IN POPS ACROSS MOST AREAS THIS AFTERNOON /ESP
THE BH/ ALTHOUGH INSTABILITY WILL BE LACKING...EVIDENT WELL IN BUFR
PROFILES. HENCE HAVE FAVORED SLIGHT CHANCE POPS MOST PLACES...SAVE
THE BH /GIVEN TERRAIN INFLUENCES/ AND SCENTRAL SD WHERE POS THETA-E
ADV AND THE STRONGEST LSA WILL OVERLAP THIS AFTERNOON. BEST
PRECIP CHANCES WILL BE THIS EVENING SCENTRAL AREAS...WHERE 40S AND
50S WERE RETAINED. OTHERWISE...SUBSIDENCE IS FAVORED OVER NW AREAS
IN NEARLY ALL GUIDANCE TONIGHT...FAVORING REMOVAL OF PRECIP CHANCES
THERE AFTER MIDNIGHT. GIVEN LACK OF APPRECIABLE INSTABILITY...PRECIP
WILL MAINLY BE IN THE FORM OF SHOWERS...WITH A FEW EMBEDDED TS
POSSIBLE. SEASONAL TO SLIGHTLY ABOVE NORMAL TEMPS EXPECTED WITH 70S
AND FEW 80S. ONGOING LL PRESSURE FALLS WILL SUPPORT A BREEZY DAY ON
THE SD PLAINS...WITH 15 TO 25 MPH WINDS EXPECTED THERE.

TUES...UPPER LOW/IMPULSE WILL SHIFT EAST WITH BACKSIDE SUBSIDENCE
SPREADING OVER THE REGION WEST-EAST. LINGERING COLD POOL ALOFT MAY
BE ENOUGH TO FORCE A FEW SHRA FROM THE BH SE INTO SCENTRAL
SD...ALTHOUGH SUPPORT FOR CONVECTION IS NOT THE GREATEST GIVEN LACK
OF APPRECIABLE LL MOISTURE AND INCREASING SUBSIDENCE. HAVE CUT POPS
ACROSS THE BOARD...WITH MAINLY SLIGHT CHANCE MENTION IN
AFOREMENTIONED AREAS. WARMER CONDITIONS EXPECTED WITH LOW 80S MOST
PLACES...SAVE THE BH AND FAR SCENTRAL SD. UPPER IMPULSE AND
ASSOCIATED PRECIP WILL DEPART THE REGION TUE NIGHT WITH DRY
CONDITIONS PREVAILING...SAVE PERHAPS A LINGERING SHOWER OVER TRIPP
COUNTY IN THE EVENING.

&&

.LONG TERM...WEDNESDAY THROUGH SUNDAY
ISSUED AT 219 AM MDT MON SEP 22 2014

DRIER AIR WILL RETURN WEDNESDAY AS A RIDGE BUILDS...AND HIGHS
WILL BE ABOVE AVERAGE FOR THE SECOND HALF OF THE WORKWEEK. THE ECM
AND GFS CONTINUE TO SHOW A SECONDARY UPPER LOW DEVELOPING AND
RETROGRADING BACK OVER THE GREAT PLAINS. HOWEVER...IT LOOKS LIKE
THE RIDGE WILL DOMINATE OUR WEATHER...SO WILL LEAVE OUT POPS
THROUGH THE END OF THE WORK WEEK. HIGH AMPLITUDE TROUGH OVER THE
WRN CONUS IS PROGGED TO REACH THE HIGH PLAINS BY NEXT
WEEKEND...BRINGING CHANCES OF SHOWERS/STORMS TO THE AREA. GFS IS
STILL QUICKER THAN THE ECM WITH THIS SYSTEM...BRINGING PRECIP IN
BY SATURDAY NIGHT.

&&

.AVIATION...FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING
ISSUED AT 219 AM MDT MON SEP 22 2014

VFR CONDITIONS ARE EXPECTED THROUGH MONDAY NIGHT. ISOLD TO SCT
-SHRA/-TSRA WILL DEVELOP ACROSS PORTIONS OF NE WY TO SW
SD THIS AFTERNOON...WITH MVFR CONDITIONS POSSIBLE IN THE HEAVIER
PRECIP. SOUTHERLY WINDS WILL BECOME BREEZY ON THE SD PLAINS.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

UPDATE...HELGESON
SHORT TERM...JC
LONG TERM...POJORLIE
AVIATION...POJORLIE



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